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Date: Sun, 29 Mar 2020 21:13:15 +0000
From: <Ludovic.Desroches@...rochip.com>
To: <Codrin.Ciubotariu@...rochip.com>, <linux-i2c@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
CC: <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
<robh+dt@...nel.org>, <peda@...ntia.se>, <linux@...linux.org.uk>,
<wsa@...-dreams.de>
Subject: Re: [PATCH v4 1/4] i2c: at91: Send bus clear command if SDA is down
On 2/25/2020 4:50 PM, Codrin Ciubotariu wrote:
> After a transfer timeout, some faulty I2C slave devices might hold down
> the SDA pin. We can generate a bus clear command, hoping that the slave
> might release the pins.
> If the CLEAR command is not supported, we will use gpio recovery, if
> available, to reset the bus.
>
> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Sounds good so
Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
Wolfram, you have accepted the v3 of the recovery support and requested
these changes. It has been sent as a v4, but, in fact, this patch goes
on top on v3. It could, should, have been a new patch.
Regards
Ludovic
> ---
>
> Changes in v4:
> - moved the HW bus clear command in a recover_bus() function, to be able
> to just call i2c_recover_bus() if a transfer fails;
> - recovery gpios are no longer taken if HW bus clear command is
> supported;
>
> Changes in v3:
> - removed unnecessary condition from info print;
> - removed unneded declarations;
>
> Changes in v2:
> - called i2c_recover_bus() after an error occurs, if SDA is down;
> - release gpios if recovery information is incomplete;
>
> drivers/i2c/busses/i2c-at91-core.c | 2 ++
> drivers/i2c/busses/i2c-at91-master.c | 49 ++++++++++++++++++++++++----
> drivers/i2c/busses/i2c-at91.h | 7 +++-
> 3 files changed, 50 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
> index 3da1a8acecb5..e14edd236108 100644
> --- a/drivers/i2c/busses/i2c-at91-core.c
> +++ b/drivers/i2c/busses/i2c-at91-core.c
> @@ -131,6 +131,7 @@ static struct at91_twi_pdata sama5d2_config = {
> .has_dig_filtr = true,
> .has_adv_dig_filtr = true,
> .has_ana_filtr = true,
> + .has_clear_cmd = false, /* due to errata, CLEAR cmd is not working */
> };
>
> static struct at91_twi_pdata sam9x60_config = {
> @@ -142,6 +143,7 @@ static struct at91_twi_pdata sam9x60_config = {
> .has_dig_filtr = true,
> .has_adv_dig_filtr = true,
> .has_ana_filtr = true,
> + .has_clear_cmd = true,
> };
>
> static const struct of_device_id atmel_twi_dt_ids[] = {
> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
> index 0aba51a7df32..776e95962ab6 100644
> --- a/drivers/i2c/busses/i2c-at91-master.c
> +++ b/drivers/i2c/busses/i2c-at91-master.c
> @@ -480,7 +480,6 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
> unsigned long time_left;
> bool has_unre_flag = dev->pdata->has_unre_flag;
> bool has_alt_cmd = dev->pdata->has_alt_cmd;
> - struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
>
> /*
> * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
> @@ -641,11 +640,12 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
> AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);
> }
>
> - if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {
> - dev_dbg(dev->dev,
> - "SDA is down; clear bus using gpio\n");
> - i2c_recover_bus(&dev->adapter);
> - }
> + /*
> + * some faulty I2C slave devices might hold SDA down;
> + * we can send a bus clear command, hoping that the pins will be
> + * released
> + */
> + i2c_recover_bus(&dev->adapter);
>
> return ret;
> }
> @@ -830,7 +830,7 @@ static void at91_unprepare_twi_recovery(struct i2c_adapter *adap)
> pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
> }
>
> -static int at91_init_twi_recovery_info(struct platform_device *pdev,
> +static int at91_init_twi_recovery_gpio(struct platform_device *pdev,
> struct at91_twi_dev *dev)
> {
> struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
> @@ -880,6 +880,41 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev,
> return 0;
> }
>
> +static int at91_twi_recover_bus_cmd(struct i2c_adapter *adap)
> +{
> + struct at91_twi_dev *dev = i2c_get_adapdata(adap);
> +
> + dev->transfer_status |= at91_twi_read(dev, AT91_TWI_SR);
> + if (!(dev->transfer_status & AT91_TWI_SDA)) {
> + dev_dbg(dev->dev, "SDA is down; sending bus clear command\n");
> + if (dev->use_alt_cmd) {
> + unsigned int acr;
> +
> + acr = at91_twi_read(dev, AT91_TWI_ACR);
> + acr &= ~AT91_TWI_ACR_DATAL_MASK;
> + at91_twi_write(dev, AT91_TWI_ACR, acr);
> + }
> + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);
> + }
> +
> + return 0;
> +}
> +
> +static int at91_init_twi_recovery_info(struct platform_device *pdev,
> + struct at91_twi_dev *dev)
> +{
> + struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
> + bool has_clear_cmd = dev->pdata->has_clear_cmd;
> +
> + if (!has_clear_cmd)
> + return at91_init_twi_recovery_gpio(pdev, dev);
> +
> + rinfo->recover_bus = at91_twi_recover_bus_cmd;
> + dev->adapter.bus_recovery_info = rinfo;
> +
> + return 0;
> +}
> +
> int at91_twi_probe_master(struct platform_device *pdev,
> u32 phy_addr, struct at91_twi_dev *dev)
> {
> diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
> index f57a6cab96b4..7e7b4955ca7f 100644
> --- a/drivers/i2c/busses/i2c-at91.h
> +++ b/drivers/i2c/busses/i2c-at91.h
> @@ -36,6 +36,7 @@
> #define AT91_TWI_SVDIS BIT(5) /* Slave Transfer Disable */
> #define AT91_TWI_QUICK BIT(6) /* SMBus quick command */
> #define AT91_TWI_SWRST BIT(7) /* Software Reset */
> +#define AT91_TWI_CLEAR BIT(15) /* Bus clear command */
> #define AT91_TWI_ACMEN BIT(16) /* Alternative Command Mode Enable */
> #define AT91_TWI_ACMDIS BIT(17) /* Alternative Command Mode Disable */
> #define AT91_TWI_THRCLR BIT(24) /* Transmit Holding Register Clear */
> @@ -69,6 +70,8 @@
> #define AT91_TWI_NACK BIT(8) /* Not Acknowledged */
> #define AT91_TWI_EOSACC BIT(11) /* End Of Slave Access */
> #define AT91_TWI_LOCK BIT(23) /* TWI Lock due to Frame Errors */
> +#define AT91_TWI_SCL BIT(24) /* TWI SCL status */
> +#define AT91_TWI_SDA BIT(25) /* TWI SDA status */
>
> #define AT91_TWI_INT_MASK \
> (AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
> @@ -81,7 +84,8 @@
> #define AT91_TWI_THR 0x0034 /* Transmit Holding Register */
>
> #define AT91_TWI_ACR 0x0040 /* Alternative Command Register */
> -#define AT91_TWI_ACR_DATAL(len) ((len) & 0xff)
> +#define AT91_TWI_ACR_DATAL_MASK GENMASK(15, 0)
> +#define AT91_TWI_ACR_DATAL(len) ((len) & AT91_TWI_ACR_DATAL_MASK)
> #define AT91_TWI_ACR_DIR BIT(8)
>
> #define AT91_TWI_FILTR 0x0044
> @@ -118,6 +122,7 @@ struct at91_twi_pdata {
> bool has_dig_filtr;
> bool has_adv_dig_filtr;
> bool has_ana_filtr;
> + bool has_clear_cmd;
> struct at_dma_slave dma_slave;
> };
>
>
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